Apparatus for testing the continuity of fuses



Feb. 19, 1952 E. c. VAN BLARCOM 2,586,125

APPARATUS FOR TESTING THE CONTINUITY OF FUSES Filed Sept. 17, 1948 55 ,57 FIG. 2

INVENTOR I EC. VAN BLARCOM ATTORNEY Patented Feb. 19, 1952 APPARATUS FOR TESTING THE CONTINUITY OF FUSES Elsworth C. Van Blarcom, Englewood, N. J., as-

signor to Western Electric rated, New York, N. Y

York

Company, Incorpoa corporation of New Application September 17, 1948, Serial N0.,49,722

6 Claims.

This invention relates to an apparatus for testing the continuity of fuses, and more particularly to apparatus for detecting swinging opens of very short duration in fuses.

Tubular types of fuses employed in the communication art occasionally contain what are commercially called swinging opens which may not be detected in commercially known test sets. By the term swinging opens, it is meant that electrically there is continuity in the fuse, but that a mechanical defect exists therein, which if the fuse is jarred or otherwise roughly handled, will cause an open in the fuse.

I-Ieretofore, test sets have been provided to jar the fuses being tested in an attempt to determine the existence of swinging opens in the fuses, but these test sets have not been sufliciently sensitive to detect an open of very short duration in a fuse under test. As a result, fuses apparently effective contained the mechanical defect of a swinging open which may become an electrical defect when installed in a communication circuit.

An object of the invention is to provide an apparatus for testing the'continuity of fuses and which is capable of detecting swinging opens in fuses under test.

With this and other objects in view, the invention comprises an apparatus for testing the continuity of fuses including terminals to removably receive and firmly hold a fuse therebetween, a

fast acting gas filled tube, the grid of which is fuse whereby continuity in the fuse will complete the circuit to cause application of a negative potential on the grid to maintain the tube unoperated. The apparatus further includes an elecdicating circuit and means rendered effective by discontinuity in the fuse removing the negative potential on the grid to cause the gas filled tube to operate to close the indicating circuit.

In the present embodiment of the invention, the apparatus also includes an agitator operated electrically to repeatedly jar a fuse under test to cause an opening of the circuit through the fuse should there exist in the fuse any mechanical defect which could cause the fuse to open while in use. There is also provided in the apparatus switch, operated with a good. fuse between the terminals, to check the efficiency of the gas tube. A timing unit is associated with the agitator limiting the time of its operation.

Other objects and advantages will be apparent from the following detailed description when considered in conjunction with the accompanying drawing, wherein Fig. 1 is a vertical sectional view of the apparatus showing a fuse under test being mounted therein; and

Fig. 2 is a wiring diagram illustrating the electrical circuits for the apparatus.

Referring now to the drawing, attention is first directed to Fig. 1 which has a supporting frame l0 upon which is mounted a fixed position terminal unit H and a movable terminal unit l2. The unit II has a terminal I4 of conductive material with a conical recess IS in the outer end thereof, the terminal being mounted for sliding movement in a sleeve is against the force of a spring [1. The spring I"! is disposed concentric with respect to a guide pin it, the reduced inner end I!) of which is threadedly connected to the terminal M. A collar 26 fixedly mounted in the opposite end of the sleeve l6 from the terminal serves as an abutment for the spring I! and is centrally apertured for longitudinal movement of the pin I8. An outer collar 2i concentric with the sleeve It supports the sleeve and its terminal mechanism and an insulating sleeve 22 is disposed concentric with the collar 2|. All of this mechanism is supported by a bracket 23 mounted at a suitable position on the main supporting frame It.

The unit I2 is substantially identical to the unit II, including a terminal 25 with a conical recess 26 slidable in a sleeve 21 against a spring 28. The sleeve 2? is disposed in a collar 29 and the collar in turn is disposed in an insulating included in a circuit with the terminals and the sleeve 30 of a bracket 3i which is mounted at any desired adjusted position in a groove 32 of the main supporting frame H1. The difference in structures of the units H and I2 lies in the mechanism for moving the terminal 25 manually trically energizable indicating element in an infor supporting a fuse 33 to be tested and freeing the fuse after test. This means includes a collar 34 having one end extending into the sleeve 2? to act as an abutment for the spring 28, the other end having a diagonally positioned surface 35. A cam 36 having a diagonally positioned surface 3'! is actuated by a lever 33 and is rotatably mounted on a rod 39 which extends through the collar 34, the spring 28, and has a reduced inner end 4!] threadedly connected to the terminal 25.

In the present embodiment of the invention, the fuse to be tested is of the tubular type shown in Fig. 1 having a tubular central portion 42 formed of insulating material and metallic ends 43 forming terminals for the fuse and connections for the fuse wire M, the continuity of which is to be tested. It will be apparent by viewing Fig. 1 that rotation of the cam 36, one half revolution, will move the terminal 25 to the left a sufficient distance against the force of the spring 28 to allow an operator space to insert a fuse to be tested between the terminals l4 and 25 after which returning the cam to its initial position will allow the springs 28 and 11 to function producing sufficient force on the ends 43 or terminals of the fuse to form satisfactory electrical connections therewith.

An agitator 46 mounted on the supporting frame I9 includes a coil 41 and a core type plunger 48 normally held downwardly by a spring 49, but positioned to strike the fuse 33 under test.

The wiring diagram illustrated in Fig. 2 discloses a fuse 33 schematically, as well as the agitator 46 and its plunger 48. The salient feature of the testing circuit includes a quick acting gas filled tube 59 which will operate as a result of a positive open or an instantaneous swinging open in the fuse caused by the agitator 46 operating during a given interval of time. Indicating elements and 52 will be energized, should there be positive discontinuity in the fuse under test.

The wiring diagram includes lead wires 55 and 56 from a 110 v. A. C. supply. A switch 51 in line 55, when closed, completes a circuit through line 55, switch 51, the winding of a relay 58 and line 56. Energization of the relay 58 closes its make contacts 59 and 60. Closing of the switch 51 also completes a circuit through a timing unit 62, this circuit being traced from line 55, through switch 51, into the timing unit at terminal 63, out of timing unit at terminal 64, through closed contact 60 to line 56 at connection 65. The timing unit 62 is of a commercially known type including a break contact 66, which is held closed during a predetermined interval of time for which the timing unit is set after which a make contact 51 of the unit is closed. The switch 51 is held closed during the entire period of the testing operation for each fuse. A circuit is therefore completed through the switch 51, through condenser and resistance 1|. in parallel, through the winding 41 of the agitator 46, through the break contact 66 of the timing unit 62, closed contact 60 and connection 65 to the line 56.

The tube 56 includes a plate 12, a grid 13, a cathode 14, and a heater 15. The heater is provided with a suitable electrical. energy, for example, 6.3 v. A. C. applied to terminals 16. The grid 13 is connected to the terminal 25 of the apparatus through a suitable resistance 18 and the terminal 14 of the apparatus is connected through a check switch 19, including contacts 80 and 9 l, to ground. The cathode 14 is maintained at a suitable potential such as 30 volts above ground by a battery 11 and as a result, the grid 13 is negatively biased to prevent the gas in the tube from breaking down providing there is c0ntinuity in the fuse 33 under test.

The contact 59 of relay 58, when closed, connects a suitable source such as a 150 volt grounded battery 63 through contact 59, resistance 84, to connection 85 between the resistance 18 in the grid circuit and the terminal 25. A relay 81, the winding of which is included in a circuit extending from connection 88 through a. resistance 89 to the plate 12 of the tube 56 is unoperated as long as there is continuity in the fuse circuit. Discontinuity in the fuse under test resulting from a positive break in the fuse wire or a defect known as a swinging open w ich will cause the fuse circuit to open while the fuse is being agitated, will disconnect the grid 13 from ground thereby removing the negative biasing potential from the grid. As soon as the bias is removed from the grid, the potential between the plate 12 and the cathode 14 is effective to break down the gas in the tube and this action is expedited by the fact that, with an open fuse, point is no longer maintained at ground potential and positive bias is applied to the grid from the source 83. The tube 59 therefore becomes and remains conducting through resistances 84 and 18 even though the fuse is open for only an extremely short time. The current in the plate circuit including the resistance 89 and the winding of the relay 81 causes the relay to operate, opening its normally closed contact 90 and closing its contact 9|. The opening of contact 90 opens the circuit through the indicating lamp 912 and the closing of contact 91 completes a circuit from conductor 94 through the indicating elements (lamp) 5| and (buzzer) 52 in parallel and conductor 91 to conductor 95. If the fuse 33 under test is good, the tube 50 does not fire, the relay 81 remains unoperated and the good condition of the fuse is indicated by the lamp 92 which is lighted after the set time interval over a circuit extending from line 94, through contact 99, lamp 92, contact 61, contact 69 to line 95. If the relay 81 had not operated, resulting from a good fuse 33 under test, a circuit would be completed through an indicating lamp 92 to indicate this condition. This circuit originates with line 94 connected to a 5 v. A. C. alternating current supply and extending through contact 90, lamp or indicating element 92, through contact 61 of the timing unit at the end of the predetermined period of time, through closed contact 60 to line 95 at connection 96.

In preparing the apparatus for operation, the units I l and 12 are positioned with respect to each other to readily receive fuses 33 of the type to be tested. Prior to inserting a fuse for test in the apparatus, for example, in the beginning of a working day, it is advisable to check the apparatus to determine whether or not the tube 59 and the indicating elements are functioning properly. This may be done readily by inserting a good fuse or an element electrically connecting the terminals 14 and 25 and then operating the check switch 19. The switch 19 is of a commercially known type capable of instantaneous operation causing the same effect resulting from a fuse with a. swinging open defect therein. The apparatus is now in readiness for operation. The operator inserts fuses 33 singly between the terminals 14 and 25 to include them in the grid circuit as shown in Fig. 2. The operator next closes the switch 51 which energizes the relay 58, causes energization of the agitator 46 and starts the timing unit 62 to function. If the fuse is satisfactory, the lamp 92 will be energized at the end of the testing interval determined by the timing unit 62. However, if there is discontinuity in the fuse, the negative potential on the grid applied through the cathode 11 is removed allowing the potential through the resistances 84 and 18 to be applied to the grid causing current flow in the plate circuit to energize the relay 81, opening the circuit to the good lamp or indicating element 92 and closing the circuits through the reject or indicating elements 5| and 52. After the indicating lamp 92 or the indicating elements 5! and 52 operate, the operator knows that the test has been completed and at this time, the switch 51 is automatically reset to test the next fuse. The same operation takes place during the testing of each fuse, first the placing of the fuse between the terminals 14 and 25 followed by the closing of the switch 51 and holding the switch closed until the test is completed.

It is to be understood that the above described arrangements are simply illustrative of the application of the principles of the invention. Numerous other arrangements may be readily devised by those skilled in the art which will embody the principles of the invention and fall within the spirit and scope thereof.

What is claimed is:

1. An apparatus for testing the continuity of fuses, comprising terminals to receive and hold therebetween a fuse to be tested, means for agitating the fuse, a gas tube having a plate, a grid and a cathode, a plate-cathode circuit for the tube including a source of potential tending to cause the tube to conduct, a grid-cathode circuit for the tube including the terminals and a source of bias potential for preventing the tube from conducting, a relay operated when the tube is conducting, a first indicator actuated when the relay is released for indicating continuity through a fuse between the terminals and'a second indicator actuated when the relay is operated for indicating a discontinuity in the fuse.

2. Apparatus according to claim 1 in combination with means responsive to a discontinuity in the grid cathode circuit for applying positive potential to the grid to accelerate the breakdown of the tube.

3. Apparatus according to claim 1 in combination with means for agitating a fuse held between the terminals, means for disabling the agitating means, and an operating circuit for the first indicator including contacts closed by the .1

operation of the disabling means.

4. Apparatus according to claim 1 having a switch in the grid-cathode circuit for momentarily opening the circuit for simulating the effect on the apparatus of a defective fuse.

is allowed to open, after which the apparatus 5. Apparatus for testing the continuity of fuses comprising means for agitating fuses to be tested, a timer for disabling the agitating means after a predetermined interval, a gas tube having a plate, a grid and a cathode, a plate-cathode circuit for the tube including a relay operated when the tube is conducting, a grid-cathode circuit including terminals for receiving and holding fuses to be tested and a source of potential for maintaining the tube in non-conducting condition, an open fuse indicator actuated by the operation of the relay, a good fuse indicator and an operating circuit therefor including contacts closed when the relay is not operated and contacts closed by the timer after the predetermined interval.

6. Apparatus for testing the continuity of fuses comprising means for agitating fuses to be tested. a gas tube having a plate, a grid, and a cathode, a plate cathode circuit for the tube including a relay operated when the tube is conducting, a grid-cathode circuit including terminals for receiving and holding fuses to be tested and a source of potential for maintaining the tube in non-conducting condition, means for disabling the agitating means, an open fuse indicator actuated by the operation of the relay, a good fuse indicator and an operating circuit therefor including contacts closed when the relay is not operated and contacts closed by the operation of the disabling means.

I ELSWORTH C. VAN BLARCOM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,882,815 Haegele et al Oct. 18, 1932 1,967,296 Dixon et al July 24, 1934 2,124,410 Cockrell July 19, 1938 2,272,239 Delmhorst Feb. 10, 1942 2,304,513 Stearns Dec. 8, 1942 2,462,326 Manoog et al Oct. 22, 1949 

